We present numerical modeling results to support the use of seafloor transient electromagnetic (EM) techniques in characterizing the buried component of active hydrothermal mounds. We construct 2D electrical models of a volcanic-hosted sulphide mound and compute the EM fields created by a transient electric dipole source deployed on the seafloor. The time it takes for fields to diffuse between the source and receivers is diagnostic of the intervening electrical conductivity. In the case considered, the highly conductive, outcropping sulphide mound is essentially invisible to the EM probe, exposing the moderately conducting alteration and upflow zone below. Transient EM responses are measurably different for the model featuring concentrated upflow compared to the model containing a spatially broad fluid supply beneath the mound.